Means for amplifying currents



L. DE FOREST.

MEANS FOR Amrugvme cunazms} APPLICATION FILED JUNE 24, I913. 7

1,375,447.; L Patented Ap -19,1 21.

2 SHEETS-SHEET I" I v DE FOREST. v MEANS FOR AMPUFYING CURRENTS.

APPLICATION FILED JUNE 24. 1913- 9 T 9 m .8 .Au n .m.

unrrso ls'rars s arsur LEE m: FOREST, OF NEW YORK, N. Y., ASSIGNOR, BY MESNE ASSIGNMENTS, TO DE FOREST RADIO TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF DELAWARE.

MEANS FOR AMPLIFYING GURRENTS.

Specification of Letters Patent.

Patented Apr. 19, 1921.

Application filed June 24, 1913. Serial No. 775,529.

1 '0 all whom it may concern..-

Be it known that 1, Ian: on Fonns'r, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Means for Amplifying Currents, of which the follow in is a full, clear, and exact specification.

This invention relates to the method of and apparatus for reproducing sounds from magnetic sound records, and to the art of reproducing magnetic sound records.

More specifically, my invention contemplates the emission of sounds by apparatus, preferably electrically controlled, from magnetic material, such as a telegraphone wire or strip, or other recordingmaterial, and preferably by the use of an audion, or audion amplifier. In accordance with my invention, the tclegraphone wire or other magnetic sound record is operated in suitable relationship to one or more magnets controlling an electrical circuit, whereby the magnetic variations corresponding to the recorded sounds, are transformed into electrical sound currents, which in turn are transformed into sound by means of a telephone receiver, a loud-speaking reproducer, or the like. I also contemplate the reproduction of sounds at a plurality of diiferent locations and more or less remotely situated from the telegraphone wire or other recording material, or other magnetized sound record, and cooperating magnet or magnets. In such form of my invention, I have found it desirable to employ a master audion for electrically controlling individual audions which are connected respectively in or control the various circuits of the various telephone receivers, loud.- speaking reproduccrs, or other means for reproducing sounds at the difi'erent locations. I record from one telegraphone wire to another, by the use of one or more audions, and cooperating circuits.

Other objects and features of my invention will be understood from the following description, and the accompanying drawin s, in whichigure 1 represents one form of my apparatus for carrying out my invention, wherein two audions are com ined for reproducing sounds recorded on a telegraphone wire;

- 15. The grid also contemplate transferring a Fig. 2 issimilar to Fig. 1, except that the circuits ot the audions are associated by means of a two coil transformer, instead of an auto-transformer;

Flg. 3 shows my method and ap aratus for reproducing sounds at a num er of different locations from a single telegraphone record;

Fig. 4 shows one form or arrangement for carrying out my method of transferring a sound record from one telegraphone wire to another telegraphone wire; and

Fig. 5 indicates another method and. apparatus for carrying out my method of reproducing sounds at a plurality of locations from a single telegraphone wire.

Referring to F'gs. 1 and 2, the telegraphone wire 1 is indicated as brought in suitable proximity to the magnets 2, 2. For such purpose, the telegra moved at asuitable .spee such as by windmg the wire 1 off of the reel 3 and onto the reel 4 by suitable mechanism, as will be understood. The magnets 2 comprise windlngs 5, 5, preferably of fine wire, arranged either in series or in parallel in the circuit comprising the conductors 6, 7. The conductor 6 is shown connected to the grid 8 of the audion 9, and the conductor '7 is shown connected to one terminal of the filament 10 of audion 9. The plate or wing 11, as indicated in Fig. 1, of audion 9 is connected through the source 12, reactance or bridging coil 13 and conductor 14 to the filament- 10. The filament 10 is shown as provided with a control circuit including the source 7 17 of audion 18 is connected to one terminal of the reactance or autotransiormer 13, the other terminal of the reactance 13 being connected to one terminal of the filament 19 of audion 18, which hone wire may be terminal of the filament 19 is connected to may be of any suitable material which becoil of transformer 16. The gri coil 13 serves plate 11 of audion 9 connected to one terminal of the filament 10 through the rimary d 17 of audion 18 is shown connected to one terminal of the secondary of the two coil transformer 16, the other terminal of said secondar being connected to one termlnal of the fi ament 19. In the case of either the auto-transformer ofFig. 1, or the two-coil transformer of Fig. 2, the action is the same,

the function is the same and the result is the same. a In both cases an electrical association is thereby accomplished-1 between the plate element of the one audion and the grid" element of the other audion, and each serves to suppl 'reactance,

pre er, in the arrangement shown m Fig. former. The primary, or secondar or both, may be constructed to be adjusta le. From the above, it will be clear that the magnetic variations recorded 1n the telegraphone wire 1 will be reproduced electrically in the form of weak undulatory else-- trio currents or impulses in the fine-wire windings 5, 5 of magnets 2, 2 and thus amplified by the audion 9, which electrical amplifications are further ampllfied by the audion 18, and thereby reproduce sounds 1n the telephone receiver, megaphone or loudspeaking reproducer, corresponding to the original sounds recorded magnetlcally on the telegraphone wire 1. By suitably controlling the temperature or energization of the filaments 10 and will be regulated and sounds controlled.

In Fig. 3, I have illustrated one form of my invention for reproducing sounds at a plurality of points distant from the point of location of a source of weak electric pulsating currents desired to be amplified, such as telegraphone currents, etc. The source of weak electric pulsating curents is schematically indicated at 25, and electrically connected to the master audion 26 through the two-coil transformer 27. The filament 28,

refer-ably of tantalum, isshown energized by the source 29, such as a storage battery. The grid 30 is connected to one terminal of the transformer 27, and the plate or wing 19, the amplification tonal quality of the 2, to'employ a one-to-one ratio trans-. 'rately controlled auxiliary audions to 31 is connected in circuit with the source 24,

and in series with the primaries 32, 33, 34, etc., of the various transformers ling the various circuits leading to the different points at which the sounds, or other indications, are -'reproduced. The secondaries 35, 36, 37, etc. are seen respectively connected to the ri of the respective laments 39 of the secondary audions 40, 41, 42, etc. As shown, the filaments 39 may be controlled by a common source, which case I prefer'to interpose the reactances or choke coils 44 between the respective terminals of the filaments 39, to thereby prevent inter-action between the secondary audions. The plates or wings 45 of the auxlliary audions are connected in the re speetive separate .circuits comprising the source 46 and operating, or controlling coil 47 of the telephone receiver, loud-speakmg reproducer, megaphone, etc. In the arrangement shown" in Fig. 3, the transformer 27 is preferably a step-up transformer to raise the voltage of the pulsating current derived at 25. The master audion oontrols 38.and one terminal- 26 operates to amplify the pulsations, which are transmitted by the transformer 27 to respective primaries 32, 33, 34 of the auxiliary audion circuits; the amplified pulsating currents are further amplified by the separeduce the desired intensity of qualit of tone or sound emitted by the telep one receiver 47, or the like. The transformers 32, 35,-33, 36,-34, 37 ,--are preferably one-toone two-coil transformers. It will be understood that the reactances or choke coils 44 may be of the adjustable type, or may be of the fixed type having a predetermined reactance. It will be clear that the telephone receivers, or the like, may be located at points remote from one another as may be desired. If a high amplification of sound is desired, two or more telephone receivers, or the like, may be connected in series in the same circuit.

In Fig. 4, I illustrate the reproducing of a magnetic sound record telegraphone wires, to thereby obtain du licate records. The master or original te egraphone Wire 50 is indicated as operated at the desired speed in suitable proximity to the telegraphone magnets 51. The magnets 51 are electrically connected to the audion, as by'means of the transformer 53. The reactance 54 is connected across the line between the audion -52'and the auxiliary audion 55, the latter controlling the o crating magnets 56 of the telegraphone 5 as by means of the transformer 58. The transformer 53 may be a stepp transformer, and the transformer 58 may be a step-downtransformer, although I may make use of a one-to-one two-coil transformer. Thus, the

pulsatin currents induced in the magnets 51, 51, Wlll be amplified by the master audion 52 and by the auxiliary audion 55, thereby producing magnetic variations in the field of the magnets 56 of the telegraphone 57 to thereby obtain a suitable magneticrecord in the wire 59.

In the particular arrangement shown, the

rimary of the transformer 53 is connected in series with the fine-wire windings of the magnets 51, 51, and the terminals of the secondary of transformer 53 are'respectively connected to the rid 60 of audion 52 and to one terminal of the filament 61, said filament being preferably of tantalum. The source 62 is connected to control the .energization of the filament 61. The wing or plate 63 of audion 52 is connected through the source 64 to one terminal of the reactance 54, the other terminal of reactance 54' being connected to the terminal of the filament 61 to which one terminal of the secondary of transformer 53 is connected. The grid 65 of audion 55 is connected through the reactance 54 with one terminal of the filament 66 of audion 55, said terminal being also connected to a terminal of the primary of transformer 58. The remaining terminal of primary of transformer 58 is connected to the source 67 and wing or plate 68 of audion 55. The filament 66 is shown controlled by a se arate source 69; however, if desired the filaments 61, 66, may be energized by a common source and suitably controlled to obtain the desired joint and individual functions.

It will also be clear that a plurality of telegraphones may be associated with res ective auxiliary audions and a master audlon, similar to the arrangement shown in Fig. 3, and thereby secure the simultaneous production of a plurality of duplicate magnetic sound records.

In accordance with the arrangement shown in Fig. 5, the weak pulsating currents are transmitted by circuit 25 through the primary of transformer 53, the secondary of which controls one or more master audions 71, 72, which in turn control local circuits, each' comprising an auxiliary audion controlling a suitable sound reproducing device. I have found that itis advantageous to form the secondary of transformer 53 of one or more coils electrically interrupted by an open-circuited gap 70. If desired, a condenser may be connected between the terminals of the conductors between which the gap exists; however, under the usual conditions, a condenser isnot necessary. The secondary of transformer 53 is connected to the grid element of audion 71 and also to one terminal of the filament ofaudion 71, the wing element of audion 71 being connected throu h primary of transformer 80 and battery 8 to said terminal of the filament 71.

terminal of the filament of audion 72. How- One terminal of secondary of transformer 80 is connected to the grid of audion 72, and the other terminal open-circuited, or, if desired connected to a condenser 84 and to one ever I have found it desirable under usual conditions to omit the condenser 84 and the said connection with the filament of audion 72. The auxiliary audions 73, 74, etc., are connected in the respective local circuits and controlled by the master audions 71, 72, prefi erably through one-to-one two-coil transformers 81, 82, the primaries of which are electrically related in parallel. I prefer to interrupt or open-circuit one of the connections of the primaries of transformers 81, 82, to thereby secure an open-circuited gap, such as that indicated at 83. The source of electrical energy 88, such as astorage battery, is shown connected between the primaries of transformers 81, 82, and one terminal of the filament of audion 72. The battery 88 ma be connected between the wing element 0 audion 72 and a primary of the transformers 81, 82. However, the interposition of the battery 88 between thefilament and the primary coils of transformers 81, 82, secures superior sensitiveness and more uniform am lification for wide ranges of tone and quallty of sounds. Similarly, the connection of source or battery 87 between the primary of transformer and the filament of audoin 71, is preferable, un-

der usual conditions of operation, as compared with the interposition of the souce 87 between the rimary of transformer 80 and the wing e ement of audion 71 The secondary of transformer 81 is connected at one end to the grid element of auxiliary audion 73, the other end of secondary 81 being open-circuited at 85. The secondary of transformer 82 is similarly connected at one end to the grid of auxiliary audion 74, and open-circuited at its other end, as indicated at 86. The local circuit oflauxiliary audion 73 is shown embodying three electromagnetic sound reproducers 91,

92, 93, the coils of which are connected in series and further connected to the wing of audion 73, battery 89 and to one terminal of the filament of audion 73. Similarl the three ele'ctroresponsive sound repro ucers .94, 95, 96, arranged in series, are connected to the wing element of audion 74, battery 90 and to one terminal of the filament of audion 74.

The respective filaments of master audions 71, 72, and of auxiliary audions 73, 74, are shown energized by a common source of electrical energy 75, such as a storage battery, and respectivel controlled by adjustable resistances 76, 7 ,7 8, 79.

It will be clear that but a single local circuit and auxiliary audion amplifier may be used, and actuated and controlled in accordance with the arrangement indicated in Fig. 5; likewise, three or more local circuits having individual audion amplifiers may be actuated and controlled by transformers arranged in arallel with respect to a master audion. hen "a plurality of electromagnetic sound reproducers are employed on a local vcircuit, such reproducers may be positioned at different locatlons in a room or auditorium, whereby sounds of any desired amplification and of highly satisfactory quality will be reproduced even from so feeble a source as a telegraphone wire.

sults in the 0 eration of my arrangement indicated 1n 1g. 5 without the use of condensers at the open-circuit gaps indicated although it is feasible to obtain amplified sounds from a telegraphone wire by the use of condensers at said open-circuited gaps. It is advantageous to arrange the gri s, of the several .audions so that the same are not connected to a source of-direct current electromotive force, and thereby markedly improve the sensitiveness of the apparatus.

I have discovered that the sensitiveness of the audion is improved by employing a plurality of grids and a plurality of wings,

preferably by'disposing each grid between a wing and thefilament. In the audion 18, see Fig. 1, I have indicated a record grid 17" disposed between the wing 20 and the filament 19, and a second wing 20 disposed to one side of the grid 17 and opposite the filament 19, so that the rid 17 is disposed between the wing 20 aniI filament 19. In a similar manner, the audions, each or all, as desired, may be provided with a plurality of grids and a plurality of wings, and thereby improve the sensitiveness of operation of the respective arrangements indicated in Figs. 1 to 5, inclusive.

From the above, it will be seen that my 'method and apparatus contemplates the transmission of relatively weak electric pulsating currents which are amplified by the use of an audion, the amplification of which is controlled independently of the strength, frequency, amplitude, etc., of the pulsating currents. Whereas, I have illustrated particular forms of my apparatus and wherein my method may be carried out, it will be understood that modifications and changes may be made therein without de arting from the scope of my invention. he circuit leads from the source of the undulatory electric currents to the first audion may be regarded and termed line wire or receptor connections, and as shown, the current fiow therein is unilateral. The audion bulbs, as shown, and as usual,

are evacuated vessels in each of which are disposed the filament, the plate or wing and the grid. In operation each filament is a cathode and when heated from the source I have secured excellent re-- I ous conducting space,

of current in circuit therewith emits negative ions. Each plate or wing is an anode and the function of the grids is to form a screen. By impressing undulatory electric currents upon the grids, as, for instance, by connecting the source of undulatory current or the receptor lead thereto, or by connecting electrically the grid or screen of one audion with the plate or anode of another, the potentials of the grids are varied correspondingly to the undulations of the currents so impressed thereon. Since the audion bulbs are evacuated the elements disposed therein are surrounded by a gaseand it is in this space between the cathode and anode elements that the ionization takes place when the cathode or filament is heated thereby forming a conducting path between the cathode and anode and in the local circuit which includes these elements and also a source of external unidirectional electro-motive force such as the batteries 12, 24:, 64, 87, 88, 89, 90. These batteries, of course serve" to maintain a difference of potential between the anodes and screens or other elements to which their terminals are connected.

In the case of Figs. 3, 4, and 5, the secondaries of transformers 27 and 53 are connected at their respective terminals to the gripor screen and filament or cathode elements, respectively, of their associated audion bulbs through leads or receptor connections in the same way as in the case of the leads 6, 7, of Figs. 1 and 2.

Having thus described my invention, what I claim as new and desire 'to secure by Letters Patent of the United States is 1. The combination with a source of weak undulatory current, of an electric circuit including a source of current, means to vary the conductivity of said circuit by and in accordance with said undulatory current, a reactance connected across said circuit, and an audion conductively connected with said circuit.

2. The combination with a source of weak undulatory current, of a vessel having therein an anode and a cathode separated from each other, and. a grid or screen, said source of undulatory current being connected to said grid or screen to Vary the conductivity of the space between said anode and cathode by and in accordance with said undulatory current, a circuit including therein said anode and cathode, and .a source of current, a second vessel containing a cathode an anode and a grid or screen, said circuit being conductively connected to said second grid or screen, a second circuit including therein said second anode and cathode and a separate source of current, and a translatelectric signals, havin in combination, an evatuated vessel, a cat ode having provision for emitting negative ions, and an anode and its screen inclosed in said vessel, a second evacuated vessel, a second cathode having provision for emitting negative ions, and a second anode means for conducting signal impulses to the first screen to vary its potential, a local circuit including a source or electromotive force and a conductive electrical connection between the first anode and second screen, and a second circu1t having a connection with a signal indicating device and including a source of electromotive force and a connection between the second cathode and second anode.

4. Apparatus for receiving or relaying electric signals, having, in combination, at least one cathode, having provision for emitting negative ions, an anode, a screen in proximity to the anode, a second anode, a second screen in proximity to the second anode, said elements being surrounded by gaseous conducting space, means for conducting the electric signal lrnpulses to the first screen to vary its potential, a local 011- cuit including a source of electromotive force and a conductive electrical connection between the first anode and second screen, and a second circuit connected with a signal indicating device and including a source of electromotive force and a connection between the second anode and a cathode.

y 5. Apparatus for receiving or relaying electric signals having, in combination, at least one cathode, a plurality of anodes and screens therefor, said elements being surrounded by gaseous conducting space, a receptor connection to one screen, a conductlve electrical connection between another screen and an anode, and a connection from another anode and a cathode to a signal indicatin device.

6. Apparatus for receiving or relaying electric signals, having, in combinatlon, an evacuated vessel, a cathode, anode and screen inclosed therein, a second evacuated vessel and a second cathode, anode and screen inclosed therein, a receptor connection to the firstscreen, a conductive electrical connection between the second screen and first anode, and a connection from the second anode and second cathode to a signal indicatin device.

7 apparatus for receiving or relaying electric signals, having, in combination, at least one cathode having provision for emitting negative ions, an anode, a screen in proximity to the anode, a second anode, a second screen in proximity to the second anode, said elements being surrounded by gaseous conducting space means for varying the potential of the first screen in response to the received signal impulses, means in-, cluding a conductive electrical connection from the first anode to the second screen and an internal unidirectional source of electromotive force in the connection for maintaining a difference of potential between the second'screen and first anode and having provision for causing variations in the potential of the second screen correspondlng to variations in the potential of the first screen and means having a connection with a signal indicating device for causing an electric current to flow between the second anode and a cathode. i

8. Apparatus for receiving or relaying electric signals, having, in combination, an evacuated vessel, a cathode having provision for emitting negative ions and an anode and its screen inclosed in said vessel, a second evacuated vessel, a second cathode having provision for emitting negative ions and a second anode and its screen inclosed in said second vessel, means for varying the potential of the first screen in-resp'onse to the received signal impulses, means including an external unidirectional source of electro-motive force for maintaining the second screen at a different potential from the second cathode and having provision for'causing variations in the potential of the second screen corresponding to variations in the potential in the first screen, and means having a connection with a signal indicating device for causing an electric current to flow between the second anode and the second cathode. i

9. Apparatus for receiving or relaying electric signals having, in combination at least one cathode having provision for emitting negative ions, an anode and its screen, a second anode and its screen, said elements being surrounded by gaseous conducting space, a connection to the first screen for causing variations in its potential corresponding to the received signal impulses, a local circuit including a connection between the first anode and second screen and a source of electromotive force for maintaining adifference of potential between the second'screen and first anode, and a connection between the second anode and a cathode including a source of electromotive force.

10. Apparatus for receiving or relaying electric slgnals, having, in combination, an evacuated vessel, a cathode having provision for emitting negative ions and an anode and its screen inclosed therein, a second evacuated vessel, and a second cathode having provision for emitting negative ions and an anode and its screen inclosed therein, a connection to the first screen'for causing variations in its potential corresponding to the received signal impulses, 'a'loeal circuit including a connection between the first anode and second screen and a source of electromotive. force for maintainin a second screen at a potential negative wit respect to the second cathode and a connection between the second anode and second cathode including a source of electromotive force.

-11. Apparatus for receiving or relaying electric signals having in combination, at least one cathode having provision for emitting negative ions, a plurality of anodes and their screens, a receiving connection to one screen, a conductive electrical connection between another screen and the anode which is adjacent the first screen, and a connection from another anode and a cathode to a signal indicating device.

12. Apparatus fofreceiving' or relaying electric slgnals, having, in combination, an evacuated vessel, a cathode having provision for emitting negative ions, and an anode and its screen in proximity to the 'cathode inclosed within said vessel, means for maintaining the screen at a negative potential with respect to the cathode by a current supplied through a similar evacuated vessel and for superimposing on said negative plotential variations in potential correspon 'ng to the signal impulses and means including a connection to a signal indicating A device for causing an electric current to flow between the cathode and anode.

13. Apparatus for receiving or relaying electric signals, having, in combination an evacuated vessel, a cathode having provision for emitting negative ions and an anode and its screen adjacent the cathode inclosed within said vessel, means tending tocause a current to flow between the anode and the cathode, means including a source of electromotive force and a partly gaseous path for normally maintaimng the screen at a potential negative with respect to the cathode, and means for causing variations in the potential of the screen corresponding to the signal impulses.

14 Apparatus for receiving or relaying electric signals, having, in combination, an evacuated vessel, a cathode having provisions for emitting negative ions and an anode and its screen inclosed in said vessel, a second evacuated vessel, a second cathode having provision for emitting negative ions and a second anode andits screen inclosed in the second vessel, means for causing variations in the potential of the first screen corresponding to the signal impulses, a circuit across the evacuated space from the first cathode to the first anode, along a wire connection to the second screen, across the evacuated space from the second screen to an adjacent electrode and back along a wire connection to the first cathode, such circuit including a source of electromotive force tending to cause a negative current to flow from the first cathode to the first anode, and a second circuit across the evacuated space from the second cathode to the second anode, said circuit including a connection to a sigtromotive'force for causing a negative current to flow from the second cathode to the second anode. I

15. Apparatus for receiving 'or relaying electric slgnals, local circuit includin a source of electromotive force, an amp ifier including a plurality of electrodes surrounded by a gaseous conductor, and connected with the local circuit and operating to produce impulses in the local circuit corresponding to but of greater intensity than the received signal lmpulses, a second circuit including a source of electromotive force and aconnection with a signal detecting device, and a second amplifier including a plurality of electrodes surrounded by a gaseous conductor, said second amplifier being conductively electrically connected with both circuits and operating to amplify the current impulses in the second circuit corresponding to but of greater intensity than the impulses in the first local circuit.

16. Apparatus for receiving or relaying electric signals, having, in combination, a local circuit including a source of electromotive force, an amplifier including a cathode, anode and screen surrounded by a gaseous conductor, said amplifier having a connection from its anode and cathode to the local circuit and a connection for leading the received impulses to its screen and operating to produce impulses in the local clrcuit corresponding to but of greater intensity than the recelved signal impulses, a second circuit including a source of electromotive force and a connection to a signal detecting device, and a second amplifier including a cathode, anode and its screen surrounded by a gaseous conductor and having its cathode and anode connected to the second local circuit and its screen conductively electrically connected to the first local circuit and operatin to amplify'the impulses in the first local clrcuit to produce impulses in the second local circuit corresponding to but of greater intensity than in the first local circuit.

17. The combination with the line wire, of apparatus for receiving or relaying electric signals transmitted ing an evacuated vessel, a cathode, anode and its screen inclosed therein, and "a unilateral connection between the apparatus and the line wire.

18. The combination, with the line wire, of apparatus for receiving or relaying electric slgnals transmitted over wires, comlprising a cathode having provision for emitting negative ions, an anode, and its screen in proximity to the cathode, said elements be ing surrounded by a gaseous conductor, a connection between the cathode and anode including a source of electromotive force,

over wires, comprisand screen inclosed therein, a connection between the cathode and anode including a source of electromotive force, a transformer having its primary in series with the line wire, and a unilateral connection between the transformer and the apparatus consist ing of a receptor connection from one terminal of the transformer secondary to the screen, the other terminal of the secondary being unconnected with the apparatus.

. 20. The combination with a magnetic sound record, means to generate .an alternating electric current by and in accordance with said record, an audion having a filament, an anode and a grid disposed therein, a circuit connection to impress said alternating current upon said grid, an energizing circuit for the filament, a second audion having a filament, an anode and a grid, a circuit connection including the anode and filament of the first audion conductively connected to the grid and filament of the second audion, and a source of current, and a local circuit including the anode and filament of the second audion and a source of current.

21. The combination witha source of ouraa'rent, of a plurality of audioms conductively connected in series, the input circuit of the first of said audions being associated with said source of current, and an independent source of current connected to the output electrode of each of said audions.

22. The combination with a source of current, of a series of audions, the .input electrode of the first of said audions in the series being associated with' said source of current, the output electrode. of the first audion of the series being conductively connected to the input electrode of the next audion of the series, and a separate source of current for the output electrode of each of said audions.

23. The combination with a source of ourrent, of a series of audions, the input electrode of the first of said audions in the series beingassociated with said source of current, the output electrode of the first audion of the series being conductively connected to the input electrode of the next audion of the series, a separate source of current for the output electrode of each of said audions, and a signal indicating device associated with the output electrode of the last audion of the series.

24. An electrical amplifying system comprising a vacuum tube device having anode and cathode electrodes, means for supplying a s ace current between said electrodes, means or controlling said space current in accordance with an impulse to be transmitted, an im edance in circuit with said electrodes, an an amplifier conductively con nected to said impedance.

25. An electrical amplifying system comprising a vacuum tube device having an anode and a cathode, an impedance, means for supplying current through said impedance and between said electrodes, means for controllin said currentin accordance with an impu se to be transmitted, an amplifierhaving an input circuit and an output circuit, said input circuit being conductively connected and responsive to the potential variations across said impedance, and a receiving device connected to said output circuit. v

26. Means for amplifying the alternating current component of a unidirectional current comprising an electron discharge device having plate and grid circuits, one of said circuits containing a source of current to be am lified, and an impedance conductively inc uded in the circuit of the source of current to be amplified and included in the grid circuit through which the current to be amplified is caused to flow.

27. Means for amplifying the alternating current component of a unidirectional current comprising an electron discharge device having plate and grid circuits, one of said circuits containing a source of current to be amplified, and a reactance conductively included in the circuit of the source of current to be amplified and included in the grid circuit through which the current to be amplified is caused to flow.

28. An electrical amplifying system com prising a vacuum tube device having anode and cathode electrodes, means for supplying a space current between said electrodes, means for controlling said space current in accordance with an impulse to be transmit ted, a reactance in circuit with said electrodes, and an amplifier conductively con-- .actance to the control circuit of another of said devices.

In testimon whereof I afiix my signature, in presence 0 two witnesses.

' LEE on FOREST.

Witnesses:

HENRY J. Loom Gno. N. Knnn. 

